This invention relates generally to axial flow harvesting machines, and more particularly, to an overlapping rasp bar rotor configuration for axial flow combines.
In conventional combine harvesters, crop material is fed between a threshing cylinder and an associated concave, whereby it is threshed over a comparatively short distance, a typical concave extending over an arc of about 100.degree.. In axial flow machines, crop material is subjected to a much longer threshing and separating action than in a conventional machine of comparable size and, therefore, the efficiency of axial flow machines is greater because grain losses are reduced.
Nevertheless, there are problems associated with axial flow machines which mitigate against this basic advantage. For example, the power requirement of an axial flow machine is greater than that of a comparable conventional machine due to the sustained threshing and separating action and difficulties can be experienced when a given machine is used to harvest different types of crop and in different conditions of crop. Clearly, it is highly desirable to provide a basic machine which can be adopted with ease to handle different types and conditions of crop. It is essential to keep grain losses to an acceptable minimum and also to achieve a smooth flow of crop material through the threshing and separating mechanisms. In the latter respect, if an amount of crop material or a piece of foreign matter ceases moving through the threshing and separating sections, a major obstruction can soon accumulate resulting in jamming or plugging of the rotor. The consequences of which can be serious in terms of down-time of the machine.
One solution to maintaining a smooth flow of crop material is a staggering of the crop threshing means, such as rasp bars, axially of a rotor, such as described in U.S. Pat. No. 4,505,279, granted to S. J. Campbell, et al on Mar. 19, 1985. While this rotor configuration provided improved performance, great operational efficiencies are still desirable.